Interaction of myo inositol hexaphosphate (MIHP) with Beta globulin from Sesamum indicum (L.).

fl-Globulin, the low molecular weight protein fraction from Sesamum indicum L., interacts with myo-inositol
hexaphosphate (MIHP) maximally at pH 3.0, with concomitant precipitation up to 85 2 2% at an MIHP
concentration of 8 x 10 - M. The kinetics of interaction as followed by stopped-flow spectrophotometry
suggested the reaction to be of pseudo first-order, having an initial fast step followed by a relatively slow step
of rate constants 1 . 9 ~ s - * , r espectively at 1 x 1 0 - 4 M~ I HP concentration. The
analysis of the complex indicated the presence of polymer as seen in sedimentation velocity experiment. This
was accompanied by conformational change of a three-fold decrease in fl-structure and also an increase in
fluorescence emission intensity accompanied with a red shift from 330 to 334 nm. Stoichiometric analysis of
MIHP binding suggested four independent binding sites for MIHP, with a free energy change, AGO = -5.1 kcal
mol- resulting from a binding constant of 3.6 x lo3 M - I .